Objects not rotating with each other (Rubik's cube)
All the small cubes of the Rubik's cube need to have their origin on the exact same point and it needs to be on the middle of the Rubik's cube. Also, when you've rotated and keyframed a face and its 6 cubes, make sure that you've also keyframed all the other cubes even if they are still, otherwise they will interpolate between other keyframes you've created for them and you may not want that.